Cooling fan question

ColoradoSteve · ColoradoSteve's Garage

I recently replaced my radiator cooling fans as one side quit working. The car is running cool but I burn up a fuse when I try to turn the AC on ( I think) and then the fans quit working and the car over- heats. Here's my question : Should both fans come on when the car reaches a certain temp or does the right side fan only come on with the AC on? I don't really care if the AC works or not, but it would be nice to have both fans blowing.Thanks!

Steve

TibetanT · TibetanT's Garage

Steve:

You should have kept the 87 Turbo!

In answer to your question, "yes" both fans should come on. If only one comes on, then that fan system is dead/bad or you may have an issue with your Fan Relay.

Is this the 1983 944 we are talking about? Thought I better ask since the later 944s have different fuse/relay boxes and location.

Hope this helps.

ColoradoSteve · ColoradoSteve's Garage

Ed,
It wasn't easy parting with the 951, but it needed someone who could give it what it needed, I just didn't have the shop to do the work. I am talking about the '83, which I have put a lot of work into and ( although it's not fast...) is still a great car and a blast to drive. Just wanted to confirm that BOTH fans should come on.
Thanks!
Steve

Toran · 08-20-2010, 11:08 PM

So on the 85.5 and later if only one of the two fans is coming on than you think the issue is likely a fan relay?

bazar01 · bazar01's Garage

Quote:

Originally Posted by ColoradoSteve

I recently replaced my radiator cooling fans as one side quit working. The car is running cool but I burn up a fuse when I try to turn the AC on ( I think) and then the fans quit working and the car over- heats. Here's my question : Should both fans come on when the car reaches a certain temp or does the right side fan only come on with the AC on? I don't really care if the AC works or not, but it would be nice to have both fans blowing.Thanks!

Steve

Here's the schematics.
1. With the engine running, when coolant temp reaches 92C, the temperature switch closes providing ground to the cooling fan relay coil closing both contacts, then both fans should run.
2. With the engine running, when the AC is turned on, the air-conditioner relay picks up providing another ground path for the cooling fan relay closing both contacts, then both fans should run.
3. With the engine off, when the coolant temperature switch still above 92C, it remains closed providing a ground path for the resistor, cooling fan motor and temperature switch, then one fan runs in slow speed until the coolant temp drops below 92C, then it stops.

962porsche · 08-21-2010, 04:38 AM

relays are very ez to test just make a jumper if the fan then comes on its the relay if not keep looking .

ColoradoSteve · ColoradoSteve's Garage

I think I have a bad AC relay( which sells for $65,). I tested the fan motors, both work and the car seems to run cool when only one is working, however, I decided that both fans should function for maximum cooling. So I wired the second fan directly to the battery, bypassing the relay. I put a switch in the center console and if the car looks like it's starting to get hot, the switch puts the fan on high and I'm cool again. Just have to remember to shut it off when I park. I suppose this is not a proper 'Porsche' fix, but it works for me....

Solid Snake · Solid Snake's Garage

The fans are kinda deceiving sometimes. I have replaced both on my 84. The last one I replaced seemed like it was working. I could plug it in with the other fan's plug and it seemed to work. What I concluded was it wasn't fully broken but the bearings in the fan get old and it takes much more power to operate it than it should. This means blown fuses and relays. I blew my A/C fan relay but I don't remember it costing $65 to replace. I wish I could remember where I got the relay. Might have been Oklahoma Foreign. Anyway, there is a great article on Clark's Garage that goes into detail about when the fans should be on and when they shouldn't. I would think that your A/C fan has bad bearings and if you replace it and the relay you will have no more problems.

smokin_944 · smokin_944's Garage

On a series 1 car, the primary fan (driver side)goes on first to start the cooling process. It runs at slow speed. The starting temp for the slow speed is determined by the thermal switch mounted in the rad on the driver side. When the engine heats up to a certain point, the driver and passenger fans kick in on high. These settings can be changed by using different value thermal fan switches.